The ancient history of Korea developed across Manchuria and the Korean Peninsula. The first Korean nation, Gojoseon, was founded in the year 2333 B.C. and lasted until the year 108 B.C. The tribal countries were founded afterward: Buyeo, Dongye, Okjeo, and Samhan. The period is called the original Three Han States Period, and the entirety of Manchuria and the Korean Peninsula were under the domain of one of the tribal countries at that time. Buyeo held power mainly over Manchuria. Dongye and Okjeo were formed in the northern and central areas of the Korean Peninsula, and the Three Han States of Mahan, Jinhan, and Byeonhan thrived on the central and southern part of the Peninsula.

 

 From the 1st century B.C. to the 1st century A.D., Goguryeo, Baekje, Silla, and Gaya were founded from succeeding and merging tribal nations. This period is referred to as the Three Kingdoms Period, when like other times, Korea’s territory stretched across Manchuria and the entire Korean Peninsula. Goguryeo occupied mainly Manchuria and the northern part of the Korean Peninsula, Silla thrived on the southern and eastern areas of the Peninsula, and Baekje dominated the southern and western regions. During the 7th century, Silla conquered both Goguryeo and Baekje, forming a unified nation on the inner region of the Peninsula, extending from Daedonggang River to Wonsanman. In 698 A.D., Balhae was founded by Goguryeo refugees. The time period is referred to as the North-South States Period.

 

 During the Goryeo Dynasty (918–1392) and the Joseon Dynasty (1392–1897), efforts to expand into the northern territories were made. By defending itself from the first invasion of Khitai in 933, Goryeo confirmed its occupation of six coastal provinces (Gangdong Yuk Ju). Goryeo started building the Great Wall (Cheolli Jangseong) in 1033 to defend its border with Khitai-Qidan. The erection of the wall established Goryeo’s northern border, stretching from Sinuiju to Hamheung, and continued its efforts to expand the northern territory until the late Goryeo Period. Such efforts lasted even into the Joseon Dynasty. As a result, in the 15th century, Joseon installed four forts in the Amnokgang Basin and six posts in the Dumangang Basin. By the establishment of these forts and posts, the territory of Joseon became the same as Korea's modern-day territory, which extends up to Amnokgang River and Dumangang River. In the 18th century, the Joseon Dynasty built the Baekdusan National Boundary Monument, marking its border with China’s Qing Dynasty.

 

 The modern and contemporary history of Korea can be summarized through a series of incidents: the establishment of the Korean Empire (1897–1910) following the Joseon Dynasty, Japanese colonial rule (1910–1945), liberation from Japan (1945), U.S. and Soviet military governments in Korea (1945–1948), and the Korean War (1950–1953). In 1897, Emperor Gojong officially declared the establishment of the Korean Empire to respond to growing international imperialism. He then carried out internal reforms only to witness the temporary loss of Korean sovereignty over its territory as it succumbed to colonial rule by Japan, whose power was strengthening over East Asia. This time period is referred to as Japanese colonial rule, which lasted until 1945. The independence movements for recovering the sovereignty of Korea never ceased, and the Korean people hailed liberation from colonial rule as Japan was defeated in the Second World War.

 

 However, the national territory was unfortunately divided into North and South along the 38th parallel north, and the division became permanent after separate governments for the North and the South were established in 1948. Korea then suffered the tragic Korean War beginning on June 25th,1950 and ending with an armistice on July 27th, 1953. The two Koreas have been in a state of truce for six decades, and those six decades have been defined largely by competition and antagonism. Despite these tensions, the two Koreas have also made sincere and meaningful efforts to build mutual trust to overcome the division, such as reunions for separated families, inter-Korean summits, and the economic cooperation at the Gaeseong Industrial Complex.

 

 Generally, in the history of Gojoseon, the period around the beginning of the common era is called the Era of the Liao River. The Liao River region was the center of competition for Koreans, Chinese, and northern powers from the 4th century B.C. to the 4th century A.D. For Korean history, it was the period when Gojoseon and Goguryeo were thriving, and when China was competing with both for the region. Korea’s first country, Gojoseon, was expanding its power and made inroads into the Liao River region, inevitably engaging in a power struggle with the Yen Dynasty of China. Gojoseon could not recover the region after it lost the region at the end of the 4th century A.D. and the state perished. Goguryeo waged a war against the Xianbei Tribe, the force that had secured the Liao River region since it was established in the 1st century B.C. Goguryeo took over the region under the reign of Great King Gwanggaeto at the end of the 4th century. During those times, the sovereignty over the Liao River Region by the two nations of Korea established a historical connection between Koreans and the Yodong Region (the eastern part of Yoha River), and this became the foundation for a series of conquests in the region.

 

 The Era of the Hangang River refers to the period from approximately the 4th to 7th century A.D. During that time, Goguryeo, Baekje, and Silla confronted each other on the river to gain power over the Korean Peninsula. The Hangang River stems from Baekdudaegan (Baekdu Mountain Range) and runs to the Yellow Sea across the Peninsula. The branches stretch to the Gwangju Mountain Range and Cheolryeong to the north, and spread around the Sobaek Mountain Range and the mountains connecting Gwangju and Eumseok. From the late 4th century to the 7th century, three nations fought to gain supremacy over the Hangang River.

 

 Baekje first occupied the Hangang River as it was raised near the river. At the end of the 4th century, Goguryeo marched down and occupied the river. The competition for territory centering on the Hangang River became fierce. Silla joined forces with the Tang Dynasty to bring down Goguryeo and Baekje. Silla discouraged the ambitious try of the Tang Dynasty to occupy the Korean Peninsula and threw the Tang foces off of the Peninsula. The unification of the country forged during that time survived through the Goryeo and Joseon Dynasties.

 

 On the other hand, 30 years after the collapse of Goguryeo, Balhae, the self-claimed successor nation of Goguryeo, was founded on the old territory of Goguryeo. Balhae made incursions into Unified Silla on the Daedonggang River for 200 years, from the late 7th century to the early 10th century. The era is called the Era of Daedonggang River, the Era of Two Nations, or the Era of Northern and Southern States. Consisting of 5 gyeongs, 15 bus, and 62 jus, Balhae had achieved remarkable land expansion since its founding. After securing the region surrounding the Songhua River and the Heilong River in Manchuria, Balhae never stopped its march south. Amid the tension, The Tang Dynasty requested that Silla attack Balhae in the early 8th century, and Silla acquiesced. Unified Silla, with nine jus and five sogyeongs, accelerated its policy to go north to the Daedonggang River area. Balhae, who was on the move south and Silla, who was marching north, met at the Daedonggang River. However, the two powers co-existed. Unlike the Era of Hangang River, the Era of Daedonggang River was not characterized by specific wars, indicating the two countries were in peaceful coexistence and were checked by the Tang Dynasty. However, early in the 10th century, the collapse of the Tang Dynasty caused chaos in the Northeastern Asian order, and during the reshuffling, Balhae collapsed. The fall of Balhae signified the loss of sovereignty over Manchuria in Korea’s history. During the same time, Unified Silla declined, and the Later Three Kingdoms Era began.